Used of human behavior, conveys that the subject is busy waiting for
someone or something, intends to move instantly as soon as it shows up, and
thus cannot do anything else at the moment. “Can't talk now, I'm
busy-waiting till Bill gets off the phone.”

Technically, busy-wait means to
wait on an event by spinning through a tight or
timed-delay loop that polls for the event on each pass, as opposed to
setting up an interrupt handler and continuing execution on another part of
the task. In applications this is a wasteful technique, and best avoided
on timesharing systems where a busy-waiting program may
hog the processor. However, it is often unavoidable
in kernel programming. In the Linux world, kernel busy-waits are usually
referred to as spinlocks.